I am using SEOChecker v1.8.1 on an umbraco 6.1.6 site. When I enable not found pages in SEOChecker and select a node as my not found page under my SEOChecker Domain settings, everything appears to work fine. I am redirected properly to my not found page. However, when I look in my umbracoTraceLogs, I see lots of errors that look like this:

2015-02-06 10:49:28,451 [7] ERROR SEOChecker.Core.Helpers.Request - [Thread 43] SEOChecker: Error could not load url http://mysite.local/1226.aspx 
System.Net.WebException: The request was aborted: The operation has timed out.
    at System.Net.HttpWebRequest.GetResponse()
    at SEOChecker.Core.Helpers.Request.GetStream(String url, HttpCookieCollection cookies, String userAgent)

Where 1226 is the node id of the Not Found Page that I selected in SEOChecker. I get these errors whenever I load any page on the umbraco site. When I unselect the Not Found Page, the errors go away. I have tried using various nodes as my 404 pages and had the same result with each. To work around the problem, I have disabled the SEOChecker not found pages and am using umbraco's default 404 page handling in the umbracoSettings.config file.

I don't know if this is related, but I occasionally get errors like this as well:

2015-02-06 08:34:46,103 [7] ERROR SEOChecker.HttpModules.UrlModule - [Thread 136] SEOChecker: Error in PageNotFound Module
System.ArgumentException: No Document exists with id '0'
    at umbraco.cms.businesslogic.web.Document.setupNode()
    at umbraco.cms.businesslogic.CMSNode..ctor(Int32 Id)
    at SEOChecker.Core.Helpers.UmbracoPreviewHelper.EnsurePreviewXml(String url, Guid previewGuid)
    at SEOChecker.HttpModules.UrlModule.(Object , EventArgs )

I checked in the SEOChecker_PageNotFound table in the database and found that nearly all of the records have a DocumentID of 0.

Anyone seen this? Any ideas? It seems like something to do with previewing because of the way that the url has http://mysite.local/1226.aspx like a preview.

Thanks